1. Field of the Invention
The present invention relates to packing boards adapted to mount an electronic device, semiconductor modules and methods of manufacturing the same.
2. Description of the Related Art
Recently, with the trend toward miniaturization and high performance of electronic devices, there is a demand for reduction of the size of semiconductor devices used in electronic devices. To achieve this, narrow-gap electrodes for external connection for semiconductor devices are essential. However, efforts for size reduction by narrowing the gap between electrodes have been successful only to a limited degree due to the constraints imposed by the size of solder bumps and solder bridges produced. Recently, there are attempts to relocate the electrodes by rewiring lines in a semiconductor device in an effort to overcome the limitation. Generally, in rewiring a semiconductor device, an aperture for via contact is formed in an insulating resin layer provided on an electrode pad, for the purpose of leading outside a signal from a semiconductor device in a semiconductor module via the electrode pad. Since a semiconductor device is disposed below an electrode pad, the aperture need be formed without applying excessive heat. However, formation of an aperture on an electrode pad by laser irradiation, as is conventionally done, involves a disadvantage in that a semiconductor device is damaged via the electrode pad due to the heat from laser, and the reliability of the semiconductor device is lowered accordingly. One method proposed to address the issue is to produce an aperture by laser irradiation and subsequent dry etching on an insulating resin layer on an electrode pad. In the related-art method of forming an aperture, an aperture is formed to a depth that does not damage a semiconductor device and the aperture is then completed by subsequent dry etching.
While the above-mentioned method can mitigate the effect from the heat produced by laser irradiation, the electrode pad, which is exposed in the final stage of dry etching will be exposed to plasma atmosphere, thus applying charge-up damage to a semiconductor device (transistor or the like) connected to the pad. Therefore, there is a concern that the device characteristics may be impaired and the reliability of a semiconductor device may be reduced. As efforts toward microfabrication of an aperture for further miniaturization of a semiconductor module are promoted in the future, the completeness of coating by the via contact formed in the aperture would be lost, and the resultant reduction in the reliability of a semiconductor module would present a problem.